Pharaoh's Ants

Scientific name: Monomorium pharaonis

How to identify pharaoh's ants

Pharaoh’s ants (Monomorium pharaonis) a species which is rare in Australia but fairly common in Europe and the USA. They form large colonies with multiple queens which can take a number of workers with them and start new colonies if disturbed by insecticides. The ants are 1.5-2.0 mm in size, light yellowish brown to darker brown in colour. They will eat protein foods plus fatty or sweet foods.

Where are pharoah ants commonly found?

They commonly nest inside buildings especially near warmer areas e.g. heating ducts.

Why are pharoah ants considered pests?

Fortunately for us, they are not generally considered to be health pests although the relatively rare Pharaoh’s ants which are often found inside hospitals are potential disease carriers as they can invade dressings of patients confined to beds and thus pose a real menace.

Some nest in decaying timber and may be suspected of actually destroying it whereas they will only infest decaying timber. Most foraging workers come from the exterior of premises but it is not particularly uncommon to find nests in roof voids, cavity walls, behind skirting boards, inside motors, inside window screens, under bath tubs, behind tiles in bathrooms and kitchens and behind taps.

In short, they like similar locations to cockroaches and as a result, control methods are very similar. Because of their nesting habits, it is common to find piles of gritty material on the floor or other horizontal surfaces or around door and window frames. On closer inspection, these piles may be found to contain dead ants which have been thrown out of the nest. No matter how often you sweep up the mess, it will re-appear as long as the ants are active.

This habit of making a little mess is not a mammoth problem but ants do become a nuisance when they are spotted walking inside pantries and getting into food containers, trailing along bench tops, window sills, skirting boards, bath tubs and invading shower recesses.

What is the biology and lifecycle of pharoah ants?

The pharaoh ant queen can lay hundreds of eggs in her lifetime. Most lay 10 to 12 eggs per batch in the early days of egg production and only four to seven eggs per batch later. At 27 °C (80 °F) and 80 percent relative humidity, eggs hatch in five to seven days. The larval period is 18 to 19 days, pre-pupal period three days and pupal period nine days. About four more days are required to produce sexual female and male forms. From egg to sexual maturity, it takes the pharaoh ant about 38 to 45 days, depending on temperature and relative humidity. They breed continuously throughout the year in heated buildings and mating occurs in the nest. Mature colonies contain several queens, winged males, workers, eggs, larvae, pre-pupae and pupae.

Management Tips For Pharaoh's Ants

Effective control depends upon a number of factors:

1. The particular species involved,

2. The location of the nest site(s) and,

3. The degree of concern they are causing the occupants.

It may be easy to control a colony with a single queen (Camponotus spp), or difficult in the case of species with multiple queens and multiple “homes” and which do not display aggression to workers from other nests (Argentine ants, Odorous house ants and Pharaoh’s ants). That is why correct identification is essential before you begin your campaign.

Ant granules were perfect for the control of some ant species to exterior areas. Most insecticide manufacturers suggest that a two-pronged approach with both baits and liquid sprays be used in order to obtain best results. These manufacturers all supply bulletins with complete instructions on how to use their products. The product labels and these bulletins should all be studied before using any of the materials.

The basic rules for the use of baits are:

• The basic premise is that bait should hopefully be consumed within 1 to 2 days when their palatability and moisture content are highest. The ants should die within 3 to 4 days.

• Correct identification – by knowing the species, you can choose the right bait for the job and can also help you find their feeding, trailing and nesting sites.

• Find the trails – you must place the bait where the ants are otherwise you are wasting time and bait. If the ants aren’t active at the time, you can pre-bait first with non-toxic foodstuffs. This will help you determine where the ants are feeding and what type of food they prefer.

• Choose the correct bait formulation, they may prefer sweet foods or protein based materials. Sometimes the same species will change food preferences depending upon seasons or other conditions. Therefore, you need to have a range of baits in your kit bag. If you just put a small blob of each bait in the ant trails, you will very soon find which they prefer.

Some key rules to observe are:

• Place the bait as close as possible to ant trails which are usually near feeding or nesting sites.

• Place adequate amounts of bait out to ensure that they will continue to feed until your next visit. By placing the bait in purpose designed “ant cafes,” you will extend the life of the bait.

• Avoid food competition by asking the client to remove available foodstuffs and liquids.

• Avoid placing gel baits near sources of heat as the gel matrix may become liquefied and moisture loss may increase. Also, avoid placing them on dry or porous surfaces which may increase water loss and make them less palatable to ants.

• Some baits lose their potency after only a few days exposure to sunlight. Make sure that you know which they are and replace them as required.

• Some granulated baits lose their potency around three months after the container has been opened. Make sure that you write on the container the date on which it was opened.

• A common piece of advice is that you mustn’t place baits on surfaces that have or will be treated with liquid or powder insecticides. Studies carried out by some researchers have indicated that this is not the case and the baits are still palatable. Some pest managers have stated, “Why waste money by applying two formulations?” and that is probably a good rule to live by. You may be able to control the ant problem without the use of insecticidal sprays and dusts but, all manufacturers recommend that bait applications are supplemented by the use of such formulations when treating free standing buildings. These insecticidal barriers will serve to prevent future ant activity to the interior.

The basic rules for the use of residual insecticide are:

• Non-repellent formulations are considered superior to repellent formulations e.g. synthetic pyrethroids, as the ants will track through the non-repellent insecticide unknowingly. Examples of non-repellent actives and formulations are Bendiocarb (Ficam), Fipronil (Termidor), Indoxacarb (Arilon), Chlorfenapyr (Phantom).

• The sprays should be applied as a barrier to the base of foundation walls, fence lines and garden beds.

• Re-application of the sprays may be necessary after rain.

• Insecticidal dusts should be applied to roof voids where practical.